This invention relates to novel pharmaceutical compositions containing desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole. These compositions possess potent antihistaminic activity and are useful in treating allergic rhinitis, asthma and other allergic disorders while avoiding adverse effects associated with the administration of other antihistamines, such as astemizole, including but not limited to cardiac arrhythmias, drowsiness, nausea, fatigue, weakness and headache. Also, these compositions, in combination with non-steroidal anti-inflammatory agents or other non-narcotic analgesics, are useful for the treatment of cough, cold, cold-like, and/or flu symptoms and the discomfort, headache, pain, fever, and general malaise associated therewith. The aforementioned combinations may optionally include one or more other active components including a decongestant, cough suppressant/antitussive, or expectorant.
Additionally, these novel pharmaceutical compositions containing desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole are useful in treating motion sickness, vertigo, diabetic retinopathy, small vessel complications due to diabetes and such other conditions as may be related to the activity of these derivatives as antagonists of the H-1 histamine receptor while avoiding the adverse effects associated with the administration of other antihistamines, such as astemizole.
Also disclosed are methods for treating the above-described conditions in a human while avoiding the adverse effects that are associated with the administration of other antihistamines, such as astemizole, by administering the aforementioned pharmaceutical compositions containing desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole to said human.
The active compounds of these compositions and methods are metabolic derivatives of astemizole. Chemically, these derivatives are desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole. These compounds are described in Kamei et al., Arzneimittel-Forschung/Drug Research, 41: 932-36 (1991).
Astemizole is an antagonist of the H-1 histamine receptor protein. Histamine receptor proteins occur in two well-identified forms in tissues, of which H-1 and H-2 receptors are two. The H-1 receptors are those that mediate the response antagonized by conventional antihistamines. H-1 receptors are present, for example, in the ileum, the skin, and the bronchial smooth muscle of man and other mammals. Astemizole antagonizes the effect of histamine in the guinea pig isolated ileum, suppresses histamine-induced whealing in the skin of guinea pigs, and protects against histamine induced bronchoconstriction in the guinea pig.
Through H-2 receptor-mediated responses, histamine stimulates gastric acid secretion in mammals and the chronotropic effect in isolated mammalian atria. Astemizole has no effect on histamine-induced gastric acid secretion, nor does it alter the chronotropic effect of histamine on atria. Thus, astemizole has no apparent effect on the H-2 histamine receptor.
Astemizole is well absorbed but is extensively metabolized. See Uchiyama et al., Pharmacometrics, 40: 77-93 (1990). Three main metabolites have been identified, and all of the metabolites are reported to have antihistaminic activity. See Kamei et al., Arzneimittel-Forschung/Drug Research, 41: 932-36 (1991).
On the basis of its antihistaminic activity, researchers evaluated the pharmacological effects of astemizole in man. Clinical trials of efficacy indicated that astemizole is an effective H-1 antagonist. See Howarth, Clin. Exp. Allergy, 20 (Suppl. 2): 31-41 (1990).
Weintraub et al., Hosp. Formul., 22: 918-27 (1987) describes clinical efficacy of astemizole in the treatment of both seasonal and perennial allergies. It has also been suggested that astemizole would be useful for the treatment of asthma.
Astemizole may also be useful for the treatment of motion sickness and vertigo. Some antihistamines have been found to be effective for the prophylaxis and treatment of motion sickness. See Wood, Drugs, 17: 471-479 (1979). Some antihistamines have also proven useful for treating vestibular disturbances, such as Meniere's disease, and in other types of vertigo. See Cohen et al., Archives of Neurology, 27: 129-135 (1972).
In addition, astemizole may be useful in the treatment of diabetic retinopathy and other small vessel disorders associated with diabetes mellitus. In tests on rats with streptozocin-induced diabetes, treatment by antihistamines prevented the activation of retinal histamine receptors which have been implicated in the development of diabetic retinopathy. The use of antihistamines to treat retinopathy and small vessel disorders associated with diabetes mellitus is disclosed in U.S. Pat. No. 5,019,591.
It has also been suggested that astemizole, in combination with non-steroidal anti-inflammatory agents or other non-narcotic analgesics, would be useful for the treatment of cough, cold, cold-like and/or flu symptoms and the discomfort, pain, headache, fever, and general malaise associated therewith. These compositions for the treatment of the above-described symptoms may optionally include one or more other active components including a decongestant (such as pseudoephedrine), a cough suppressant/antitussive (such as dextromethorphan) or an expectorant (such as guaifenesin).
Many antihistamines cause somewhat similar adverse effects. These adverse effects include but are not limited to sedation, gastrointestinal distress, dry mouth, and constipation or diarrhea. Astemizole has been found to cause relatively less sedation as compared with other antihistamines. See Weintraub et al., Hosp. Formul., 22: 918-27 (1987).
However, the administration of astemizole to a human has been found to cause other adverse effects. These adverse effects include but are not limited to cardiac arrhythmias, including ventricular tachyarrhythmias, torsades de pointes, and ventricular fibrillation. See Knowles, Canadian Journal Hosp. Pharm., 45: 33,37 (1992); Craft, British Medical Journal, 292: 660 (1986); Simons et al., Lancet, 2: 624 (1988); and Unknown, Side Effects of Drugs Annual, 12: 142 and 14: 135. An additional unwanted side effect of astemizole is appetite stimulation and weight gain in patients taking the drug for various indications. See Krstenansky et al., Drug Intell. Clin. Pharm., 21: 947-53 (1987).
Thus, it would be particularly desirable to find a compound with the advantages of astemizole which would not have the aforementioned disadvantages.